Bitmap

1. Avoid using BitmapFactory.createBitmap to create Bitmap object.
2. Using BitmapFactory.decodeStream to create Bitmap , because the decodestream method is using JNI nativeDecodeAsset without android platform.
3. Using Bitmap.recycle() to recycle bitmap memory when you don't need the image.
4. Using BitmapFactory.Options and inJustDecodeBoundsattribute

public static Bitmap decodeSampledBitmapFromResource(String imagePath, int reqWidth, int reqHeight) {

    // First decode with inJustDecodeBounds=true to check dimensions
    final BitmapFactory.Options options = new BitmapFactory.Options();
    options.inJustDecodeBounds = true; 
    options.inPreferredConfig = Bitmap.Config.RGB_565;  // Replacing image quailty by image memory
    BitmapFactory.decodeFile(imagePath, options);

    // Calculate inSampleSize
    options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);

    // Decode bitmap with inSampleSize set
    options.inJustDecodeBounds = false;
    return BitmapFactory.decodeFile(imagePath, options);
}

public static int calculateInSampleSize(
            BitmapFactory.Options options, int reqWidth, int reqHeight) {
        // Raw height and width of image
        final int height = options.outHeight;
        final int width = options.outWidth;
        int inSampleSize = 1;

        if (height > reqHeight || width > reqWidth) {

            final int halfHeight = height / 2;
            final int halfWidth = width / 2;

            // Calculate the largest inSampleSize value that is a power of 2 and keeps both
            // height and width larger than the requested height and width.
            while ((halfHeight / inSampleSize) > reqHeight
                    && (halfWidth / inSampleSize) > reqWidth) {
                inSampleSize *= 2;
            }
        }

        return inSampleSize;
    }